1. Field of the Invention
The present invention relates to a discharge recovery device for maintaining and recovering ink-discharging performance of a recording head that performs recording by discharging ink onto a recording medium, and to an ink-jet recording apparatus including the discharge recovery device.
2. Description of the Related Art
Ink-jet recording apparatuses perform recording by discharging ink onto a recording medium. Since ink is discharged from fine discharging outlets of a recording head, the discharging outlets are sometimes clogged by ink thickened due to an increase in dye concentration in the ink and fixing of the ink due to evaporation of a volatile component. Moreover, bubbles are sometimes produced in an ink chamber of the recording head. Bubbles interfere with normal ink supply operations. In the worst case, ink does not flow to the recording head, which seriously hinders recording.
In order to prevent such problems, some ink-jet recording apparatuses use a discharge recovery device that maintains and recovers ink-discharging performance by unclogging the recording head. The discharge recovery device includes, for example, a cap for covering a discharging surface of the recording head, a suction unit for sucking ink from the discharging outlets by producing a negative-pressure state inside the cap covering the discharging outlets, a wiper for wiping foreign materials, such as ink, off the discharging surface of the recording head, and a wiper cleaner for removing the foreign materials transferred to the wiper.
In these ink-jet recording apparatuses, in general, the discharging surface is wiped by utilizing the motion of a carriage on which the recording head is mounted. That is, a wiper-retracting mechanism (mechanism for moving the wiper into and out of contact with the discharging surface) is provided, and the carriage is moved with the wiper protruding only when needed so that the discharging surface is wiped in a direction orthogonal to rows of discharging outlets (horizontal wiping). In this case, since the wiper is away from the discharging surface when being retracted, it does not interfere with a scanning motion of the recording head during recording. In this wiping method utilizing the motion of the carriage, the wiper can be provided as a relatively simple structure.
In an ink-jet recording apparatus having a recording head in which a plurality of discharging-outlet rows corresponding to a plurality of color inks are arranged side by side in the scanning direction of the recording head (the moving direction of the carriage), since the above-described horizontal wiping means sequentially wipes the discharging-outlet rows, ink wiped off the preceding discharging-outlet row is forced into the succeeding discharging-outlet row, and consequently, inks of different colors are prone to be mixed. A vertical wiping means for moving a wiper parallel to discharging-outlet rows is used to prevent color mixture. In vertical wiping, however, it is also difficult to reliably clean the discharging surface with the wiper that remains soiled with ink. In order to maintain high cleaning performance of the wiper, a wiper-cleaning means is provided to scrape ink off the wiper with a wiper cleaner (e.g., an edge of a mold) after cleaning of the discharging surface.
However, when the wiper passes the wiper cleaner, ink adhering to the wiper may scatter and soil the interior of the apparatus because of elastic bending of the wiper and a returning motion of the wiper. In particular, when the wiper cleaner is used for the above-described vertical wiping, scattering ink sometimes adheres to, for example, a carriage guide and an encoder scale, which adversely affects normal recording operation. As a means for preventing this problem, U.S. Pat. No. 5,984,452 discloses a wiping method using a wiper cleaner that can pivot in one direction. In this method, the wiper cleaner is fixed when cleaning the wiper, and is pivoted by using kinetic energy of the wiper during a backward movement of the wiper.
In the disclosed method, however, the wiper is bent to counter the biasing spring force holding the wiper cleaner at a predetermined position. Therefore, ink sometimes scatters because of a returning force that is produced at the moment when the wiper separates from the wiper cleaner. The amount of scattering ink can be reduced by setting the biasing spring force extremely small or utilizing the weight of the wiper cleaner without the spring. In these methods, however, the wiper cleaner sometimes does not return to the normal position. Recently, an increasing number of ink-jet recording apparatuses have been using pigment-based ink having higher density and higher water resistance. However, the pigment-based ink thickens easier than dye-based ink.
For this reason, in a recording apparatus using pigment-based ink, when the ink reaches a pivot shaft of the wiper cleaner, the pivotal motion of the wiper cleaner is hindered, the wiper cleaner is not sufficiently returned to the normal position, and wiping performance is reduced. In order to overcome these problems, a sufficient biasing spring force must be ensured so that the wiper cleaner stably returns to the normal position even when ink adheres thereto. That is, the problem in ink scattering during wiper cleaning cannot be fundamentally solved by adjusting the biasing spring force of the wiper cleaner. Therefore, the art disclosed in the above publication cannot prevent ink scattering during wiper cleaning.